How many bones do we have at birth?

If you've ever seen a real skeleton or fossil in a museum, you might think that all bones are dead. Although bones in museums are dry, hard, or crumbly, the bones in your body are different. The bones that make up your skeleton are all very much alive, growing and changing all the time like other parts of your body.

A baby's body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults have. Some of a baby's bones are made entirely of a special material called cartilage (say: KAR-tel-ij). Other bones in a baby are partly made of cartilage. This cartilage is soft and flexible. During childhood, as you are growing, the cartilage grows and is slowly replaced by bone, with help from calcium.

By the time you are about 25, this process will be complete. After this happens, there can be no more growth — the bones are as big as they will ever be. All of these bones make up a skeleton that is both very strong and very light.

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Where is 25% of human bones?

There are 206 bones in an adult human's body. We have 26 bones in each foot. So our feet consist of 52 bones, which amount to more than 25%. Not surprisingly, our feet support our entire body's weight and allow us to jump, run, and climb. Those bones and joints also enable our feet to absorb and release energy efficiently.


The skeletal structure of the foot is similar to that of the hand but, because the foot bears more weight, it is stronger but less movable.

The bones of the foot are organized into the tarsal bones, metatarsal bones, and phalanges.

The foot begins at the lower end of the tibia and fibula, the two bones of the lower leg. At the base of those, a grouping of bones form the tarsals, which make up the ankle and upper portion of the foot.

There are five metatarsal bones in each foot. Similar to the bones of the hand, these nearly parallel bones create the body of the foot. Numbered one through five, the bone that sits behind the big toe is number one, and the one behind the little toe is number five.

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Why is the mucus/phlegm green when you have an infection?

If you see green or yellow phlegm, it’s usually a sign that your body is fighting an infection. The color comes from white blood cells. At first, you may notice yellow phlegm that then progresses into green phlegm. The change occurs with the severity and length of the potential sickness.

If you've ever stopped to look at the contents of the tissue after you've blown your nose, you may have noticed that your mucus isn't always perfectly clear. It may be yellow, green, or have a reddish or brownish tinge to it. What do those colors mean?

You might have heard that yellow or green mucus is a clear sign that you have an infection, but despite that common misperception, the yellow or green hue isn't due to bacteria.

When you have a cold, your immune system sends white blood cells called neutrophils rushing to the area. These cells contain a greenish-colored enzyme, and in large numbers they can turn the mucus the same color.

Mucus can also contain tinges of reddish or brownish blood, especially if your nose gets dried out or irritated from too much rubbing, blowing, or picking. Most of the blood comes from the area right inside the nostril, which is where most of the blood vessels in the nose are located. A small amount of blood in your mucus isn't anything to worry about, but if you're seeing large volumes of it, call your doctor.

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What is bronchitis?

Bronchitis is when the tubes that carry air to your lungs, called the bronchial tubes, get inflamed and swollen. You end up with a nagging cough and mucus.

Most often, the same viruses that give you a cold or the flu cause acute bronchitis. But sometimes, bacteria bring it on.

In both cases, as your body fights the germs, your bronchial tubes swell and make more mucus. That means you have smaller openings for air to flow through, which can make it harder to breathe.

Your doctor usually can tell whether you have bronchitis based on a physical exam and your symptoms. They’ll ask about your cough, such as how long you’ve had it and what kind of mucus comes up with it. They’ll also listen to your lungs to see whether anything sounds wrong, like wheezing.

Your doctor may need to do some tests, depending on whether they think you have acute or chronic bronchitis.

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Which is the part of the respiratory system that takes air from the trachea to the lungs?

The bronchi are the airways that lead from the trachea into the lungs and then branch off into progressively smaller structures until they reach the alveoli, the tiny sacs that allow for the exchange of oxygen and carbon dioxide in the lungs.

Primary bronchi are located in the upper portion of the lungs, with secondary bronchi near the center of the lungs. Tertiary bronchi are located near the bottom of these organs, just above the bronchioles. No gas exchanges occur in any of the bronchi. When the bronchi become swollen due to irritants or infection, bronchitis results and makes breathing more difficult. Bronchitis sufferers also tend to have much more mucus and phlegm than someone without inflamed bronchi.

The secondary bronchi continue to branch off to form the tertiary bronchi, which are further divided into terminal bronchioles.

There are as many as 30,000 tiny bronchioles in each lung. They lead to the alveoli (tiny air sacs where the exchange of carbon dioxide and oxygen occurs) by way of alveolar ducts.

Together, the trachea and the two primary bronchi are referred to as the bronchial tree. At the end of the bronchial tree lie the alveolar ducts, the alveolar sacs, and finally the alveoli.

The tubes that make up the bronchial tree perform the same function as the trachea. They distribute air to the lungs.

The alveoli are primarily responsible for exchanging carbon dioxide and oxygen, which occurs in the lungs.

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